Single quantum emitters (SQEs) are at the heart of quantum optics1 and photonic quantum-information technologies2. To date, all the demonstrated solid-state single-photon sources are confined to one-dimensional (1D; ref. 3) or 3D materials4,5,6,7. Here, we report a new class of SQEs based on excitons that are spatially localized by defects in 2D tungsten-diselenide (WSe2) monolayers. The optical emission from these SQEs shows narrow linewidths of ∼130 μeV, about two orders of magnitude smaller than those of delocalized valley excitons8. Second-order correlation measurements revealed a strong photon antibunching, which unambiguously established the single-photon nature of the emission9. The SQE emission shows two non-degenerate transitions, which are cross-linearly polarized. We assign this fine structure to two excitonic eigenmodes whose degeneracy is lifted by a large ∼0.71 meV coupling, probably because of the electron–hole exchange interaction in the presence of anisotropy10. Magneto-optical measurements also reveal an exciton g factor of ∼8.7, several times larger than those of delocalized valley excitons11,12,13,14. In addition to their fundamental importance, establishing new SQEs in 2D quantum materials could give rise to practical advantages in quantum-information processing, such as an efficient photon extraction and a high integratability and scalability.
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This work is supported by the National Natural Science Foundation of China, the Chinese Academy of Sciences and the National Fundamental Research Program. The work at the University of Washington is supported by the Air Force Office of Scientific Research (FA9550-14-1-0277). G.C. is partially supported by the State of Washington through the University of Washington Clean Energy Institute. X.X. thanks the Cottrell Scholar Award for support. W.Y. is supported by the Croucher Foundation (Croucher Innovation Award) and the Research Grants Council of Hong Kong (HKU705513P, HKU9/CRF/13G).
The authors declare no competing financial interests.
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He, Y., Clark, G., Schaibley, J. et al. Single quantum emitters in monolayer semiconductors. Nature Nanotech 10, 497–502 (2015). https://doi.org/10.1038/nnano.2015.75
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